1. The Field of the Invention
The following relates generally to image processing and more particularly to a method and system for compensating for perceived motion blur in digital video hold-type displays.
2. The Relevant Technology
Moving objects in digital video displayed on a hold-type display device such as a liquid crystal display (LCD) can appear blurry to an observer. The perceived blur is caused in part by the relatively slow “LC response” of the liquid crystal cells. When compared with an impulse-type device such as a cathode ray tube (CRT) device, for example, an LCD device has a much slower brightness transition response time. The perceived blur is also caused in part by prolonged light emission inherent in the sample-and-hold driving technique commonly employed by LCD devices, which results in formation of after-images on the human retina. These after-images produce a blurred visual perception as the video sequence is being observed.
Turning to FIG. 1, a schematic diagram showing perceived blur in a digital video image frame resulting from the LCD device and the motion perception mechanisms of the human visual system is shown. As an input video sequence is input to a LCD device, each digital video image, or frame, from the input video sequence is displayed and sustained on the LCD device for one frame interval. While viewing a scene in motion, the human eyes actively track the scene with smooth pursuit eye movement so as to generate a stabilized image on the human retina, as described by M. J. Hawken and K. R. Gegenfurtner in the publication entitled “Pursuit Eye Movements to Second Order Motion Targets” (Journal of the Optical Society of America A, 18(9), pp 2292-2296, 2001). The human visual system then undertakes visual temporal low pass filtering in order to perceive a flicker-free image.
FIGS. 2a to 2d are frame and timing diagrams showing the tracking behavior of the human eye that results in perceived blur in the digital video image. FIG. 2a shows a typical frame in two dimensions. FIG. 2b shows the horizontal position of one scanline in the frame of FIG. 2a as a function of time. FIG. 2c shows the motion compensated position of the scanline after the human eye has tracked its movement. It can be seen that the same light pattern is periodically imaged on the retina resulting in somewhat steady state vision. FIG. 2d shows the frame in motion as perceived by the human visual system, as a result of integration over one frame interval. It can be seen that the frame as perceived is blurry. It can therefore be seen that the combination of the LCD device and the tracking behavior of the human visual system results in a spatial low pass filtering effect, i.e., motion blur.
Numerous methods have been proposed to compensate for motion blur. One method is to insert a black frame between each pair of frames in a frame sequence. This method essentially simulates an impulse display, which does not suffer perceived motion blur problems. However, an overall reduction in brightness results from implementation of this method. Alternatively, video pre-processing may be applied to frames of the digital video sequence prior to display on the hold-type device. Video pre-processing methods that presently exist have certain drawbacks, however, such as high computational cost, loss of resolution, or artifacts such as false motion edges and frame juddering.
Given these and other drawbacks, it would be desirable to provide a novel method and system that compensates for perceived motion blur in digital video and that does so in a manner that minimizes computational cost, loss of resolution, and undesired side-effects such as false motion edges or frame juddering.